selftests/bpf: Add IRQ save/restore tests

Include tests that check for rejection in erroneous cases, like
unbalanced IRQ-disabled counts, within and across subprogs, invalid IRQ
flag state or input to kfuncs, behavior upon overwriting IRQ saved state
on stack, interaction with sleepable kfuncs/helpers, global functions,
and out of order restore. Include some success scenarios as well to
demonstrate usage.

#128/1   irq/irq_save_bad_arg:OK
#128/2   irq/irq_restore_bad_arg:OK
#128/3   irq/irq_restore_missing_2:OK
#128/4   irq/irq_restore_missing_3:OK
#128/5   irq/irq_restore_missing_3_minus_2:OK
#128/6   irq/irq_restore_missing_1_subprog:OK
#128/7   irq/irq_restore_missing_2_subprog:OK
#128/8   irq/irq_restore_missing_3_subprog:OK
#128/9   irq/irq_restore_missing_3_minus_2_subprog:OK
#128/10  irq/irq_balance:OK
#128/11  irq/irq_balance_n:OK
#128/12  irq/irq_balance_subprog:OK
#128/13  irq/irq_global_subprog:OK
#128/14  irq/irq_restore_ooo:OK
#128/15  irq/irq_restore_ooo_3:OK
#128/16  irq/irq_restore_3_subprog:OK
#128/17  irq/irq_restore_4_subprog:OK
#128/18  irq/irq_restore_ooo_3_subprog:OK
#128/19  irq/irq_restore_invalid:OK
#128/20  irq/irq_save_invalid:OK
#128/21  irq/irq_restore_iter:OK
#128/22  irq/irq_save_iter:OK
#128/23  irq/irq_flag_overwrite:OK
#128/24  irq/irq_flag_overwrite_partial:OK
#128/25  irq/irq_ooo_refs_array:OK
#128/26  irq/irq_sleepable_helper:OK
#128/27  irq/irq_sleepable_kfunc:OK
#128     irq:OK
Summary: 1/27 PASSED, 0 SKIPPED, 0 FAILED

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241204030400.208005-8-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 444 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/irq.c b/tools/testing/selftests/bpf/progs/irq.c
new file mode 100644
index 000000000000..b0b53d980964
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/irq.c
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+
+unsigned long global_flags;
+
+extern void bpf_local_irq_save(unsigned long *) __weak __ksym;
+extern void bpf_local_irq_restore(unsigned long *) __weak __ksym;
+extern int bpf_copy_from_user_str(void *dst, u32 dst__sz, const void *unsafe_ptr__ign, u64 flags) __weak __ksym;
+
+SEC("?tc")
+__failure __msg("arg#0 doesn't point to an irq flag on stack")
+int irq_save_bad_arg(struct __sk_buff *ctx)
+{
+	bpf_local_irq_save(&global_flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("arg#0 doesn't point to an irq flag on stack")
+int irq_restore_bad_arg(struct __sk_buff *ctx)
+{
+	bpf_local_irq_restore(&global_flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_2(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags2);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_3(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags2);
+	bpf_local_irq_save(&flags3);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_3_minus_2(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags2);
+	bpf_local_irq_save(&flags3);
+	bpf_local_irq_restore(&flags3);
+	bpf_local_irq_restore(&flags2);
+	return 0;
+}
+
+static __noinline void local_irq_save(unsigned long *flags)
+{
+	bpf_local_irq_save(flags);
+}
+
+static __noinline void local_irq_restore(unsigned long *flags)
+{
+	bpf_local_irq_restore(flags);
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_1_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags;
+
+	local_irq_save(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_2_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+
+	local_irq_save(&flags1);
+	local_irq_save(&flags2);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_3_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save(&flags1);
+	local_irq_save(&flags2);
+	local_irq_save(&flags3);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("BPF_EXIT instruction in main prog cannot be used inside bpf_local_irq_save-ed region")
+int irq_restore_missing_3_minus_2_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save(&flags1);
+	local_irq_save(&flags2);
+	local_irq_save(&flags3);
+	local_irq_restore(&flags3);
+	local_irq_restore(&flags2);
+	return 0;
+}
+
+SEC("?tc")
+__success
+int irq_balance(struct __sk_buff *ctx)
+{
+	unsigned long flags;
+
+	local_irq_save(&flags);
+	local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__success
+int irq_balance_n(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save(&flags1);
+	local_irq_save(&flags2);
+	local_irq_save(&flags3);
+	local_irq_restore(&flags3);
+	local_irq_restore(&flags2);
+	local_irq_restore(&flags1);
+	return 0;
+}
+
+static __noinline void local_irq_balance(void)
+{
+	unsigned long flags;
+
+	local_irq_save(&flags);
+	local_irq_restore(&flags);
+}
+
+static __noinline void local_irq_balance_n(void)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save(&flags1);
+	local_irq_save(&flags2);
+	local_irq_save(&flags3);
+	local_irq_restore(&flags3);
+	local_irq_restore(&flags2);
+	local_irq_restore(&flags1);
+}
+
+SEC("?tc")
+__success
+int irq_balance_subprog(struct __sk_buff *ctx)
+{
+	local_irq_balance();
+	return 0;
+}
+
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+__failure __msg("sleepable helper bpf_copy_from_user#")
+int irq_sleepable_helper(void *ctx)
+{
+	unsigned long flags;
+	u32 data;
+
+	local_irq_save(&flags);
+	bpf_copy_from_user(&data, sizeof(data), NULL);
+	local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
+__failure __msg("kernel func bpf_copy_from_user_str is sleepable within IRQ-disabled region")
+int irq_sleepable_kfunc(void *ctx)
+{
+	unsigned long flags;
+	u32 data;
+
+	local_irq_save(&flags);
+	bpf_copy_from_user_str(&data, sizeof(data), NULL, 0);
+	local_irq_restore(&flags);
+	return 0;
+}
+
+int __noinline global_local_irq_balance(void)
+{
+	local_irq_balance_n();
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("global function calls are not allowed with IRQs disabled")
+int irq_global_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags;
+
+	bpf_local_irq_save(&flags);
+	global_local_irq_balance();
+	bpf_local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("cannot restore irq state out of order")
+int irq_restore_ooo(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags2);
+	bpf_local_irq_restore(&flags1);
+	bpf_local_irq_restore(&flags2);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("cannot restore irq state out of order")
+int irq_restore_ooo_3(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags2);
+	bpf_local_irq_restore(&flags2);
+	bpf_local_irq_save(&flags3);
+	bpf_local_irq_restore(&flags1);
+	bpf_local_irq_restore(&flags3);
+	return 0;
+}
+
+static __noinline void local_irq_save_3(unsigned long *flags1, unsigned long *flags2,
+					unsigned long *flags3)
+{
+	local_irq_save(flags1);
+	local_irq_save(flags2);
+	local_irq_save(flags3);
+}
+
+SEC("?tc")
+__success
+int irq_restore_3_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save_3(&flags1, &flags2, &flags3);
+	bpf_local_irq_restore(&flags3);
+	bpf_local_irq_restore(&flags2);
+	bpf_local_irq_restore(&flags1);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("cannot restore irq state out of order")
+int irq_restore_4_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+	unsigned long flags4;
+
+	local_irq_save_3(&flags1, &flags2, &flags3);
+	bpf_local_irq_restore(&flags3);
+	bpf_local_irq_save(&flags4);
+	bpf_local_irq_restore(&flags4);
+	bpf_local_irq_restore(&flags1);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("cannot restore irq state out of order")
+int irq_restore_ooo_3_subprog(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags2;
+	unsigned long flags3;
+
+	local_irq_save_3(&flags1, &flags2, &flags3);
+	bpf_local_irq_restore(&flags3);
+	bpf_local_irq_restore(&flags2);
+	bpf_local_irq_save(&flags3);
+	bpf_local_irq_restore(&flags1);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("expected an initialized")
+int irq_restore_invalid(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+	unsigned long flags = 0xfaceb00c;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("expected uninitialized")
+int irq_save_invalid(struct __sk_buff *ctx)
+{
+	unsigned long flags1;
+
+	bpf_local_irq_save(&flags1);
+	bpf_local_irq_save(&flags1);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("expected an initialized")
+int irq_restore_iter(struct __sk_buff *ctx)
+{
+	struct bpf_iter_num it;
+
+	bpf_iter_num_new(&it, 0, 42);
+	bpf_local_irq_restore((unsigned long *)&it);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("Unreleased reference id=1")
+int irq_save_iter(struct __sk_buff *ctx)
+{
+	struct bpf_iter_num it;
+
+	/* Ensure same sized slot has st->ref_obj_id set, so we reject based on
+	 * slot_type != STACK_IRQ_FLAG...
+	 */
+	_Static_assert(sizeof(it) == sizeof(unsigned long), "broken iterator size");
+
+	bpf_iter_num_new(&it, 0, 42);
+	bpf_local_irq_save((unsigned long *)&it);
+	bpf_local_irq_restore((unsigned long *)&it);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("expected an initialized")
+int irq_flag_overwrite(struct __sk_buff *ctx)
+{
+	unsigned long flags;
+
+	bpf_local_irq_save(&flags);
+	flags = 0xdeadbeef;
+	bpf_local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("expected an initialized")
+int irq_flag_overwrite_partial(struct __sk_buff *ctx)
+{
+	unsigned long flags;
+
+	bpf_local_irq_save(&flags);
+	*(((char *)&flags) + 1) = 0xff;
+	bpf_local_irq_restore(&flags);
+	return 0;
+}
+
+SEC("?tc")
+__failure __msg("cannot restore irq state out of order")
+int irq_ooo_refs_array(struct __sk_buff *ctx)
+{
+	unsigned long flags[4];
+	struct { int i; } *p;
+
+	/* refs=1 */
+	bpf_local_irq_save(&flags[0]);
+
+	/* refs=1,2 */
+	p = bpf_obj_new(typeof(*p));
+	if (!p) {
+		bpf_local_irq_restore(&flags[0]);
+		return 0;
+	}
+
+	/* refs=1,2,3 */
+	bpf_local_irq_save(&flags[1]);
+
+	/* refs=1,2,3,4 */
+	bpf_local_irq_save(&flags[2]);
+
+	/* Now when we remove ref=2, the verifier must not break the ordering in
+	 * the refs array between 1,3,4. With an older implementation, the
+	 * verifier would swap the last element with the removed element, but to
+	 * maintain the stack property we need to use memmove.
+	 */
+	bpf_obj_drop(p);
+
+	/* Save and restore to reset active_irq_id to 3, as the ordering is now
+	 * refs=1,4,3. When restoring the linear scan will find prev_id in order
+	 * as 3 instead of 4.
+	 */
+	bpf_local_irq_save(&flags[3]);
+	bpf_local_irq_restore(&flags[3]);
+
+	/* With the incorrect implementation, we can release flags[1], flags[2],
+	 * and flags[0], i.e. in the wrong order.
+	 */
+	bpf_local_irq_restore(&flags[1]);
+	bpf_local_irq_restore(&flags[2]);
+	bpf_local_irq_restore(&flags[0]);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";